Molecular genotyping, adhesion and biofilm formation in methicillin-resistant Staphylococcus aureus clinical strains

Abstract number: P1851

Gherardi G., Pomponio S., Visaggio D., Pompilio A., Dicuonzo G., Angeletti S., Creti R., Baldassarri L., Di Bonaventura G.

Objectives: In the present study we evaluated the correlation between methicillin resistance and biofilm formation in S. aureus clinical isolates.

Methods: A total of 36 methicillin-resistant (MRSA) and 73 methicillin-susceptible (MSSA) S. aureus clinical strains from different source of isolation were genotyped by Pulsed-Field Gel Electrophoresis (PFGE). Resistance to methicillin was confirmed by the detection of the mecA gene. Adhesion to and biofilm formation on polystyrene were evaluated by the microtiter plate assay in aerobic, microaerophilic (5% CO2), and anaerobic atmospheres.

Results: Twenty-one different PFGE types were identified. A total of 8 and 16 PFGE types were found among MRSA and MSSA, respectively, while 3 were shared by both groups. Among PFGE types shared by more than 5 isolates, PFGE types 1 and 15 were identified only in MRSA, while PFGE types 2, 3, 7, 10 and 14 consisted only of MSSA. Among PFGE types shared by both groups, MRSA isolates predominated in PFGE type 4, while MSSA were more prevalent in PFGE types 5 and 6.

Biofilm level formed in anaerobiosis was significantly lower than that observed under aerobic and microaerophilic conditions (p < 0.001), either comparing MRSA and MSSA or within MRSA strains. Overall, MRSA did not differ from MSSA with regard to adhesion and biofilm levels, regardless of atmosphere tested. However, significant differences in biofilm formation in aerobiosis was observed among specific PFGE groups including MRSA strains. In particular, MRSA strains belonging to PFGE type 4, comprising also MSSA isolates, formed significantly more biofilm than that observed in MRSA isolates belonging to other PFGE types and to MSSA strains of the same group. No difference in adhesion levels was observed among pulsotypes.

Conclusion: Specific PFGE types represented by MSSA or MRSA were found, thus suggesting that certain MRSA and MSSA isolates segregate in different genetic lineages. Overall, MRSA and MSSA strains do not differ in adhesion and biofilm formation. Nevertheless, a clonal group of MRSA, defined by PFGE 4, exhibited a significant increased ability in forming biofilm with respect to other PFGE groups comprising MRSA as well as to all MSSA isolates.

Session Details

Date: 07/05/2011
Time: 00:00-00:00
Session name: Abstracts of 21st ECCMID / 27th ICC
Location: Milan, Italy, 7 - 10 May 2011
Presentation type:
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